The market for mushrooms continues to grow each year. This is due to an increasing interest in the culinary, nutritional and health benefits of mushrooms. The commercial production of mushrooms, however, is a complex procedure. It involves a series of steps including compost preparation, compost pasteurization, inoculating the compost with spawn, incubation to allow colonization of the compost with mushroom mycelia, pinning and cropping. Contamination with a pathogenic agent at any of these stages can result in serious yield losses.
The term “mushroom” is used herein to refer to various types of mushrooms. This includes the most familiar cultivated mushroom, Agaricus bisporus and also includes other types of mushrooms such as oyster mushrooms, crimini mushrooms, portobello mushrooms and shitake mushrooms, just to mention a few.
A major threat to successful large scale mushroom production is green mold. Green mold is caused by infestation with Trichoderma. Various types of Trichoderma spp. can result in a green mold infestation. A particularly pathogenic strain, identified as Trichoderma harzianum biotype 4, was responsible for a large green mold epidemic in the United States during the 1990's. When spawned mushroom beds are infested with Trichoderma spp. mold, non productive areas occur on the casing surface resulting in serious yield losses. Compost infestation can result in green sporylation which can turn into black patches uncolonized by mushroom mycelia.
Various attempts have been made to control infestation with green mold. For example, U.S. Pat. No. 6,061,951 describes a mushroom bed cover. The invention described therein involves the use of a cover which includes a series of holes or vents that are selected to control the CO2 rates and oxygen rates during spawning so as to lower the rate of green mold. While this cover may reduce the rates of green mold infestation, it does not completely prevent it. In addition there may be other disadvantages associated with covering the beds including excessively high CO2 content and over heating of the compost.
Another attempt at controlling green mold is described in U.S. Pat. No. 5,762,928. This patent describes the use of a composition comprising Pseudomonas aeruginosa which can be applied to compost, spawn or supplement to prevent or inhibit the growth of green mold. While the Pseudomonas composition was shown to have some effect in inhibiting green mold, the use of Pseudomonas as a large scale deterrent for green mold is not feasible since Pseudomonas is associated with several pathogenic states in humans.
While biocontrol agents have been shown to have some success in preventing mold on certain types of plants, control of mold in mushroom production provides a unique challenge. Since mushrooms, like mold, are fungi, agents that kill contaminating mold may also adversely affect the mushrooms.
Thus, there remained an unmet need for an agent that can control green mold without adversely affecting production of the mushrooms. The agent should also be safe for human consumption.